Spark plug with central electrode attachment member containing platinum or platinum alloy

Abstract

A sparking plug with a central electrode insulated in respect of the plug screw-thread and with earth electrodes which are electrically connected to the plug screw-thread, there being at the combustion chamber end of the central electrode an attachment part which consists at least partially of platinum or a platinum alloy, the spark gaps being disposed between it and the earth electrodes which extend to it from the side. According to the invention, the attachment part takes the form of a prism, the top surface of which faces the combustion chamber. Furthermore, the earth electrodes extend laterally alongside the side faces of the substantially prismatic attachment member parallel with the edges of top or base surfaces of the prism. This ensures considerable stability and low burn-off. Furthermore, the electrode gap can easily be adjusted.

We claim: 
     
       1. A sparking plug comprising: a central electrode; a plug screw-thread insulated from said central electrode; and earth electrodes electrically connected to said plug screw-thread; said central electrode having an end, on which is disposed an attachment member consisting at least partially of platinum or a platinum alloy, with spark gaps disposed between said attachment member and said earth electrodes, said earth electrodes extending laterally along side faces of said attachment member; said attachment member being further characterized in that it has the form of a prism, with a top and a base surface, said top surface having diagonal dimensions in the range of a diameter of said central electrode, said top surface facing the combustion chamber of said central electrode, and in that the earth electrodes extend laterally along said side faces of said attachment member and substantially parallel with edges of said top or base surface of said prism. 
     
     
       2. The sparking plug according to claim 1, characterized in that the top surface of the attachment member is at right-angles to the longitudinal axis of the central electrode. 
     
     
       3. The sparking plug according to claim 1, characterized in that the base surface of the attachment member bears at least partially on the combustion chamber end of the central electrode. 
     
     
       4. The sparking plug according to claim 1, characterized in that said attachment member further comprises a central bore which is aligned with a bore in said central electrode, said bores being filled with a fused-in metal or a fused-in metal alloy, particularly hard solder, to connect said attachment member to said central electrode. 
     
     
       5. The sparking plug according to claim 1, characterized in that the base surface of the attachment member is directly connected to the combustion chamber end of the central electrode. 
     
     
       6. The sparking plug according to claim 1, characterized in that the attachment member takes the form of a right prism. 
     
     
       7. The sparking plug according to claim 1, characterized in that the base surface or top surface of the attachment member is rectangular, and is preferably square. 
     
     
       8. The sparking plug according to claim 1, characterized in that the base surface or top surface of the attachment member is triangular.